Are you sure your glow plugs are working and how long are you energizing them before you try to start it?
You may need to do a compression test. Have you adjusted the valves?
Have you done the diesel upgrades yet? They make a huge difference in starting them.
Gear reduction starter
https://www.onlycubcadets.net/forum/showthread.php?t=1
Glow plug upgrade
Get (3) NGK 2031 (Y-103V) and rewire them using a solenoid. Lots of posts on OCC doing that.